Countdown star Rachel Riley has joked about staying away from the game show's letter tiles, after she spelt out a rude word on screen.

The 29-year-old presenter laughed nervously as she put up the letters S, L, U and T in Monday's episode of Channel 4's words and numbers competition.

Things got even more awkward when she also turned over a Z, as she urged host Nick Hewer to move on, saying: "Let's speed this along."

The incident, which Riley dubbed an "occupational hazard", got laughs from contestant Chris Reeves as well as the studio crowd, but the University of Oxford graduate maintained her professionalism throughout.